Conventional networks typically include data communications devices that transmit data packets from one or more sources to one or more destinations. Data communications devices, such as routers, receive packets containing data and control information at input ports, and, based on destination or other information included in the packets, route the packets to appropriate output ports that lead to either another router or to the packet's final destination. Certain networks, such as Voice Over Internet Protocol (VOIP) networks, include multiple powered devices such as Internet-Protocol telephones (IP telephones) connected by one or more routers. These VOIP networks allow the IP telephones to send and receive audio, video, data, and other signals as Internet-Protocol signals.
The VOIP network can provide power to the IP telephones using a power source, such as a Power over Ethernet (PoE) device. For example, IP telephones typically connect to a router using RJ-45 connectors having four pairs of twisted pair conductors used to transmit data. In the VOIP networks, the PoE device injects power between the router and the IP telephones and transmits the power over the conductors of the RJ-45 connectors.
In use, the power source transmits a particular amount of power to the powered device based upon the power classification of the powered device as defined by the IEEE 802.3af standard. In one arrangement, IP telephones, such as IP telephones models 7960G, 7961G, 7970G, or 7971 G-GE manufactured by Cisco Systems, Inc. of San Jose, Calif., each receive a particular amount of power from the PoE device during operation based upon the power classification of the telephone.